Given trapezoid ABCD, what is the length of ?

Answer:
XY = 18 units.
Step-by-step explanation:
The sum of the top and bottom lines = 2 * middle line, so:
6x + 1 + s = 2(4s - 2)
7s + 1 = 8s - 4
5 = s.
So XY = 4(5) - 2 = 18.